/*
===========================================================================
Copyright (C) 1999-2005 Id Software, Inc.
Copyright (C) 2000-2006 Tim Angus

This file is part of Tremulous.

Tremulous is free software; you can redistribute it
and/or modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the License,
or (at your option) any later version.

Tremulous is distributed in the hope that it will be
useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Tremulous; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
===========================================================================
*/

#include "cg_local.h"

/*
===============
CG_RunLerpFrame

Sets cg.snap, cg.oldFrame, and cg.backlerp
cg.time should be between oldFrameTime and frameTime after exit
===============
*/
void CG_RunLerpFrame(lerpFrame_t * lf)
{
	int             f, numFrames;
	animation_t    *anim;

	// debugging tool to get no animations
	if(cg_animSpeed.integer == 0)
	{
		lf->oldFrame = lf->frame = lf->backlerp = 0;
		return;
	}

	// if we have passed the current frame, move it to
	// oldFrame and calculate a new frame
	if(cg.time >= lf->frameTime)
	{
		lf->oldFrame = lf->frame;
		lf->oldFrameTime = lf->frameTime;

		// get the next frame based on the animation
		anim = lf->animation;
		if(!anim->frameLerp)
			return;				// shouldn't happen

		if(cg.time < lf->animationTime)
			lf->frameTime = lf->animationTime;	// initial lerp
		else
			lf->frameTime = lf->oldFrameTime + anim->frameLerp;

		f = (lf->frameTime - lf->animationTime) / anim->frameLerp;
		numFrames = anim->numFrames;
		if(anim->flipflop)
			numFrames *= 2;

		if(f >= numFrames)
		{
			f -= numFrames;
			if(anim->loopFrames)
			{
				f %= anim->loopFrames;
				f += anim->numFrames - anim->loopFrames;
			}
			else
			{
				f = numFrames - 1;
				// the animation is stuck at the end, so it
				// can immediately transition to another sequence
				lf->frameTime = cg.time;
			}
		}

		if(anim->reversed)
			lf->frame = anim->firstFrame + anim->numFrames - 1 - f;
		else if(anim->flipflop && f >= anim->numFrames)
			lf->frame = anim->firstFrame + anim->numFrames - 1 - (f % anim->numFrames);
		else
			lf->frame = anim->firstFrame + f;

		if(cg.time > lf->frameTime)
		{
			lf->frameTime = cg.time;
			if(cg_debugAnim.integer)
				CG_Printf("Clamp lf->frameTime\n");
		}
	}

	if(lf->frameTime > cg.time + 200)
		lf->frameTime = cg.time;

	if(lf->oldFrameTime > cg.time)
		lf->oldFrameTime = cg.time;

	// calculate current lerp value
	if(lf->frameTime == lf->oldFrameTime)
		lf->backlerp = 0;
	else
		lf->backlerp = 1.0 - (float)(cg.time - lf->oldFrameTime) / (lf->frameTime - lf->oldFrameTime);
}
